secret things

A. First, let’s examine what each verse says.
• Deut 29:29 The secret things belong to the LORD our God, but the things revealed belong to us and to our sons forever, that we may observe all the words of this law.

The “secret things” are contrasted with “the things revealed”. They are the things God chose to keep to Himself.
• Acts 1:7 He said to them, “It is not for you to know times or epochs which the Father has fixed by His own authority;

The context of Deut 29 is the renewal of the covenant, about the blessings when Israel obeys and curses when Israel disobeys. So more specifically the “secret things” concern Israel’s future which is contingent upon her obedience.

The “things revealed” parallel “the words of this law” in the last part of v29. They belong to us & to our descendents forever, as God’s laws are abiding, so that we may observe them.

• Prov 25:2 It is the glory of God to conceal a matter, but the glory of kings is to search out a matter.

God gets glory when men realize their limitations in failing to understand His universe or the way He rules it:
• Rom 11:33-36 Oh, the depth of the riches both of the wisdom and knowledge of God! How unsearchable are His judgments and unfathomable His ways! For WHO HAS KNOWN THE MIND OF THE LORD, OR WHO BECAME HIS COUNSELOR? Or WHO HAS FIRST GIVEN TO HIM THAT IT MIGHT BE PAID BACK TO HIM AGAIN? For from Him and through Him and to Him are all things. To Him be the glory forever. Amen.

Kings get glory when they discern the truth & administer justice:
• 1 Kgs 3:9 So give Your servant an understanding heart to judge Your people to discern between good and evil. For who is able to judge this great people of Yours?
Properly understood, I don’t see any contradiction between these verses. As God, He has a right to disclose some things to us and conceal others from us. Generally speaking, the concealed things He reserved for Himself concern the future, except in the case of prophecies He chose to reveal, as proof of His sovereignty:
• Isa 21:43 Declare the things that are going to come afterward, That we may know that you are gods;

Within the subset of what He reveals, including His laws which reflect His nature, it is up to kings or rulers to understand His will, so that they can carry out His will & govern in accordance to His character. There is no conflict & perfect harmony between the 2 verses.